ZOOLOGY: G. N. CALKINS 
97 
be recovered from the cysts until they have been dried for some weeks. 
The process of reorganization, therefore, cannot escape observation, and it has 
never occurred in the isolation cultures. The uniformity of results in all 
of the series outlined below, is sufficient evidence that no other method of 
asexual reorganization, or parthenogenesis, has occurred in any isolation 
culture. 
A single ex-conjugant from a pair of 'wild' conjugating individuals was 
isolated on Nov. 24, 1917. It formed the parental series, or, as I shall call 
it, the 'A series' and I would explicitly state again, that all results described 
here, have been obtained with lineal descendants, by division, of this one 
ancestral cell, and without change of the culture medium.* Five lines were 
established at the third division and the relative vitality, at successive ten-day 
periods, is shown in column 1 of table 1. The series ran through 313 gen- 
erations by division and died out after a long period of progressively reduced 
vitality, on September 18, 1918. 
Conjugation tests were made every week and gave constant epidemics 
of pairing after the first six weeks. A single pair of conjugating individuals 
was isolated on four different occasions. In each case the pair was watched 
until the two individuals had separated. One of the ex-conjugants on each 
occasion, was then isolated as the starting individual of a filial series. The 
first of these ex-conjugants formed the filial C series and came from a pair 
which were in the 78th generation of the parent A series, on February 4, 1918. 
The second, formed the filial D series which came from a pair of the A series 
conjugating on March 8, 1918, in the 137th generation. The third, formed 
the filial H series, which came from a pair conjugating on May 17, 1918, in 
the 237th generation of the parent A series. The fourth formed the fihal J 
series which came from a pair conjugating on August 12, 1918, in the 311th 
generation of the parent A series. The parent A series died from exhaustion 
in the 313th generation, hence these four filial series were taken off at dif- 
ferent periods of waning vitality of the parent protoplasm. Each was main- 
tained in five lines and treated exactly like the parent isolation series. Their 
histories, in successive ten-day periods, are shown in columns 2, 3, 4 and 5. 
The history of the C series was similar to that of the parent A series. After 
a long period of progressively reduced vitality it died on December 31, 1918, 
in the 348th generation. The D series outlived the parent series but did not 
live as long, dying after 230 days in the 271st generation. The H series is 
still alive and is now (January 8, 1919) in the 277th generation. The J series 
was taken from the parent A series when vitality of the latter was very 
low, each individual of the parent series dividing only 2.2 times in ten days. 
The effect of conjugation, as shown by the J series was to increase the divi- 
sion rate to 17.2 times in ten days, while, for the same calendar period, the 
parent series was dividing at the rate of two-tenths of one division in ten 
days. The J series is still dividing actively in the 236th generation. 
* At the present time (March 15) descendants are still living with unimpaired vigor. 
